Digitizer systems are well known to those skilled in the art. Typically, an electromagnetic digitizer array, or other type of system, is responsive to a stylus used by a user to enter data directly upon the digitizer array and to control various computer functions by writing, sketching, or pointing the stylus against the digitizer array. Some examples of digitizer systems locate the digitizer array directly on a monitor and other examples separate the two devices. Usually, the separate digitizer systems are utilized where a relatively large work surface is needed when compared to the size of the display device such as a monitor screen. Integrated digitizer and display devices are utilized where portability and size are important. As such, various types of computer systems utilize stylus-based technologies and may include portable systems, desktop systems, transportable, or terminal-based systems.
The integrated digitizer-display systems are integrated only in the sense that they are coplanar and are fitted together with a monitor or display in a common device. They are not integrated in that a signal processor is required to convert the signals generated by the digitizer into display signals compatible with the display. Thus, additional circuitry is involved in even the simplest of digitizer-display systems that are integrated for direct input to the same display surface where the digitizer is located.
In addition to requiring additional circuitry, another disadvantage of conventional digitizer systems is excessive energy consumption. For example, conventional digitizer systems typically require the digitizing array to always be powered to receive input from a user's stylus. Furthermore, the user must also save the input information to long-term storage, such as a hard disk drive or other energy-consuming non-volatile memory on the computing system, in order to preserve the input information. Excessive power consumption tends to increase costs and may reduce the battery lifetime if the digitizer system is provided in a portable computing system.